Method and fabric for pipe reinforcement

ABSTRACT

A fabric for reinforcing concrete pipe including longitudinally expandable circumferential defining strands at the female or bell-forming end of the fabric. A cage formed of such fabric can be expanded outwardly at the bell end to define the enlarged bell. Stiffeners are joined to the longitudinally expandable circumferential defining strands and to the first two nonexpandable circumferential defining strands to provide a restraint against the collapse of the bell end of the cage once it is cast in concrete and weight is placed thereon. Both corrugated and closed loop expandable circumferentials are disclosed. Where stiffeners or longitudinals are joined to opposite sides of a closed loop, they include a generally Sshaped deviation capable of compression as the sides of the loop move towards one another during expansion of the loops. Where longitudinals or stiffeners are joined to the nodes of corrugated circumferentials, they are provided with generally S-shaped deviations which facilitate movement of those nodes during expansion of the corrugated circumferentials. Where stiffeners extend across a loop but are joined to only one side thereof, and the longitudinals are joined intermediate the loops, the longitudinals are provided with deviations which allow freer movement of the free sides of the loops towards the joined sides of the loops as the closed loop circumferentials are expanded.

llnited States Patent 1 Tolliver 1111 3,844,510 1451 Oct. 29, 1974 METHOD AND FABRIC FOR PIPE REINFORCEMENT [75] Inventor: Wilbur E. Tolliver, Holland, Mich.

[73] Assignee: New York Wire Mills C0rp.,

Tonawanda, NY.

[22] Filed: Feb. 8, 1973 21 Appl. N0.2 330,606

[52] US. Cl 245/1, 138/175, 140/107 [51] Int. Cl B211 27/00 v {58] Field of Search 245/1, 2, 3, 5, 7, 8, 9, 245/11; 140/107, 112; 52/664; 138/175, 176, 173, 140,143,145,153

[56] v References Cited UNITED STATES PATENTS 939,567 11/1909 Thun 138/125 950,264 2/1910 Hugo 138/175 2,004,409 6/1935 Hopkins 140/112 3,254,681 6/1966 Magers 140/112 3,342,003 9/1967 Frank 52/664 3,396,761 8/1968 Laswell 140/112 3,437,114 4/1969 Whitacre et a1. 1 140/112 3,578,036 5/1971 Francois 140/107 3,744,529 7/1973 Jorda et al. 138/125 Primary Examiner-C. W. Lanham Assistant Examiner-James R. Duzan Attorney, Agent, or Firm-Price, Heneveld, Huizenga & Cooper [57] ABSTRACT A fabric for reinforcing concrete pipe including longitudinally expandable circumferential defining strands at the female or bell-forming end of the fabric. A cage formed of such fabric can be expanded outwardly at the bell end to define the enlarged bell. Stiffeners are joined to the longitudinally expandable circumferential defining strands and v to the first two nonexpandable circumferential defining strands to provide a restraint against the collapse of the bell end of the cage once it is cast in concrete and weight is placed thereon. Both corrugated and closed loop expandable circumferentials are disclosed. Where stiffeners or longitudinals are joined to opposite sides of a closed loop, they include a generally S-shaped deviation capable of compression as the sides of the loop move towards one another during expansion of the loops. Where longitudinals or stiffeners are joined to the nodes of corrugated circumferentials, they are provided with generally S-shaped deviations which facilitate movement of those nodes during expansion of the corrugated circumferentials. Where stiffeners extend across a loop but are joined to only one side thereof, and the longitudinals are joined intermediate the loops, the longitudinals are provided withdeviations which allow freer movement of the free sides of the loops towards the joined sides of the loops as the closed loop circumferentials are expanded.

Claims, 8 Drawing Figures PATENIEUum 29 1924 3.844510 SHEU 1 0f 4 Q AAYK 1 AW AV F/az METHOD AND FABRIC FOR PIPE REINFORCEMENT BACKGROUND OF THE INVENTION The present invention relates to wire fabric for reinforcing concrete pipe. Such fabric normally is a network of wire strands. When rolled into a cylindrical cage, the wire strands extending the length of the cage are usually called longitudinals and those encircling the cage are called circumferentials. Some refer to the longitudinal wires'as weft" wires and the circumferential wires as warp wires.

The reinforcing cages are formed either circularly or elliptically with one enlarged end. The enlarged end is called the bell end of thefabric. When the cage is formed and cast in concrete, the enlarged or bell end receives the non-enlarged or spigot end of a succeeding pipe.

One technique for forming the bell end in a wire cage involves the use of non-rectilinear, for example corrugated, circumferential stra'nds at the bell end of the fabric. After the cage is formed, the corrugated strands are expanded radially 'outwardlyJThey straighten to some extent and thereby form the enlarged bell end.

One drawback to this method is that when stress forces are placed on the pipe, the corrugations or nonrectilinear deformations tend to straighten still further, I

thereby allowing the concrete to crack. When the pipe is buried in theground, the weight of the dirt compressing the pipe tends to force the bell end to stretch outwardly to either side. The resulting forces of tension on the corrugated circumferentials tend to straighten them and thereby cause the concrete to crack.

I have conceived several new pipe reinforcing fabrics which minimize such cracking while still allowing one to form a bell by expanding the bell end of a cylindrical cage outwardly. In my copending application Ser. No. 330,510, entitled METHOD AND FABRIC FOR PIPE REINFORCEMENT, I describe a fabric employing circumferential strands comprised of a plurality of interconnected'closed loops. These loops can be expanded during formation of thebell, but the entrapment of concrete therein prevents their further expansion afterthe pipe is formed. In my copending patentapplication SerQNo. 330,609, entitled FABRIC AND METHOD FOR FORMING PIPE REINFORCEMENT, I disclose a fabric in which corrugated circumferential strands are joined by tie members disposed intermediate adjacent-longitudinal defining'strands. While the corrugated strands .are free to expand during formation of the bell, the tie members act as anchorsonce the bell is cast in concrete to thereby minimize further expansion of the, corrugations afterthe pipe is formed. The present i'nventioncomprises yet another fabric which minimizes cracking. The present invention can be used inconjunction with my other fabric inventions or in conjunction with prior'art fabrics. v l I SUMMARY or THE INVENTION In the present invention, stiffeners are joined to longitudinally expandable circumferentials at the bell forming end of the fabric and to at least the first, and preferably the first two non-expandable circumferential defining strandsof the. fabric. These stiffeners are generally shorter than the longitudinal defining strands and are interposed between adjacent longitudinal-deinvention are joined to the closed loop defining strands intermediate the loops. In this way, they do not interfere with longitudinal expansion of the loops. In the alternative, either the stiffeners or the longitudinals ex tend across loops and are joined to both sides of agiven' loop, but include a compressible deviation disposed within the loop such that the sides of the loop are allowed to compress inwardly towards one another when,

the closed loop strand is expanded longitudinally.

In yet another aspect of this invention, the longitudinal or stiffener which extends across a particular closed loop is joined to only one side of the loop, the other side of the loop beingfree to move towards the joined side. Those longitudinals or stiffeners which are joined to the closed loop strands intermediate the closdloops include deviations which expand orcontract to facilitate such movement of the free sides of the loop towards the joined sides of the loops.

In yet another aspect of this invention, where the Iongitudinally expandable circumferentials are corrugated strands, those of the stiffeners or longitudinals which are joined to the nodes of the corrugated strands in clude compressible or expandable deviations therein. These deviations allow movement of the nodes either inwardly or outwardly with respect to the rest of the fabric when the corrugated, circumferentials are expanded. 7

These and other features, objects and advantages of my invention will be more fully understood and appreciated by reference to the written specification and ap pended drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a plan view of the bell end and the next sucembodiment of my invention;-

FIG. 6 is a similar plan view of yet another alternative embodiment'of my invention;

FIG. 7 is a similar planview of yet another alternative embodiment of my invention; and

FIG. 8 is a similar plan view of yet another alternative embodiment of my invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT In the embodiment shown in FIG. 1, the fabric 1 comprises. a plurality of circumferential defining strands 20 joined to a plurality of longitudinal defining strands 10 in a conventional manner. Two longitudinallyexpandable closed loop circumferential strands 30 are welded to the longitudinals 10- at the bellforming end of the fabric. A plurality of stiffeners 50 are welded to the closed loop circumferentials 30 and to the first two next adjacent non-longitudinally expandable circumferential defining wires 20. These stiffeners 50 provide added ridigity to the bell of a formed cage and thereby resist the tendency for the bell to collapse after it has been cast in a pipe, or after it has been buried in the ground.

The longitudinal defining strands and the circumferential defining strands are so denominated because when the fabric is formed into a cylindrical cage, the longitudinal defining strands 10 will extend the length thereof and the circumferential defining strands 20 will extend around the circumference thereof. These strands are wire. They are welded to one another in a conventional fashion.

The closed loop circumferential strands may comprise strands of expanded metal, or may be formed by welding together two corrugated strands of wire in back-to-back fashion. A plurality of interconnected closed loops 31 are defined. The construction of the closed loop strands and the manner in which they resist expansion after being cast in concrete is more fully set forth in my copending patent application Ser. No. 330,5I0, entitled METHOD AND FABRIC FOR PIPE REINFORCEMENT.

The stiffeners 50 are preferably somewhat stiffer than the longitudinal defining strands 10. They may comprise a stiffer wire or they may comprise lengths of bar stock. Rebar provides exceptional stiffness and reinforcing strength.

The stiffeners 50 are welded to the circumferential defining strands 20 and closed loop circumferential defining strands on the same side as are the longitudinal defining strands 10. It is preferable that when the cage is formed, it is formed with the stiffeners and longitudinal defining strands 10 to the inside of the cage. In this manner, the stiffeners 50 provide greater supportive strength.

It is preferable that the stiffeners 50 be welded at least to the first two non-longitudinally expandable circumferential defining strands 20. They then provide a very rigid bridge or support for the longitudinally expandable closed loop circumferentials 30. They also serve as anchors for the fabric when embedded in concrete.

In fabric 1 of the FIG. I embodiment, the longitudinal defining strands l0 and the stiffeners 50 are joined to the closed loop circumferentialstrands 30 at points intermediate the interconnected closed loops. In this manner, the closed loops are free to collapse during expansion of the strands 30 without interference from the attached stiffeners 50 or longitudinal defining strands l0.

The term expandable" or -longitudinally expandable" as used hereinrefers to the capability of a strand to be expanded sufficiently readily and to a sufficient degree to make possible the formatiom of an enlarged bell end on the cylindrical cage. Naturally any strand of wire is to some extent longitudinally expandable" in the strictest interpretation of this term. However, one skilled in the art will appreciate that the term as used herein requires that the strand be capable of being expanded longitudinally on itself a sufficient degree to facilitate bell formation. Thus, the closed loop circumferentials 30 which are capable of a substantial amount of elongation are referred to as longitudinally expandable strands while the ordinary circumferential defining strands 20 which are capable of only a slight amount of stretching are referred to as nonexpandable or non-longitudinally expandable" strands.

The fabric 2 of the embodiment of the invention shown in FIG. 2 is comparable to the fabric shown in FIG. 1, except that the closed loops 31 are larger and the longitudinal defining strands 10 extend across certain of the closed loops 31 (FIG. 2). Each longitudinal 10 is welded to each closed loop 31 at each of the opposite sides thereof. In order to minimize the tendency for such a construction to resist elongation of the loops,

31, the longitudinal defining strands 10 are provided with generally S-shaped deviations 11 within each closed loop 31. These S-shaped deviations 11 are collapsible and thereby tend to collapse as forces of longitudinal elongation are placed on closed loop circumferentials 30. The collapsing of S-shaped deviations 11 allows the opposite sides of closed loops 31 to collapse towards one another. As in the fabric 1 of FIG. 1, the stiffeners 50 are joined to the closed loop circumferentials 30 intermediate the adjoining loops 31.

The fabric 3 of FIG. 3 is similar to the fabric 2 of FIG. 2, except that the stiffeners 50 extend across the closed loops 31 of closed loop circumferentials 30. In effect, the longitudinals 10 and stiffeners 50 are reversed with respect to their positions in the fabric 2 of FIG. 2. In fabric 3, the stiffeners 50 are provided with generally S-shaped deviations 51 which operate in the same manner as the S-shaped deviations ll of fabric 2 of FIG. 2.

The fabric 4 of FIG. 4 is comparable to that disclosed in FIG. 1 except that the stiffeners 50 extend across closed loops 31 and are welded to only one side of each loop. The points of welding are indicated by Xs. The circles indicate that a side is free to slide along the length of stiffener 50. Thus, as a closed loop circumferential 30 is elongated, the free side of the loop slides along stiffener 50 towards the welded side.

Another difference in fabric 4 is that the longitudinal defining strands 10 are provided with generally U- shaped deviations 12. These deviations 12 facilitate expansion of the longitudinals 10 at the bell-forming end of the fabric such that the free sides of the closed loops 31 more readily travel towards the welded sides thereof.

In the fabric 4 as shown, the closed loops 31 are welded to the stiffeners 50 on the outsides thereof, i.e., away from the rest of the fabric and away from the nonexpandable circumferentials 20. Thus, the closed loop circumferentials 30 tend to move outwardly with respect to the rest of the fabric as they are elongated. In the broader aspects of the invention, this situation could be reversed and the closed loops 31 could be welded to the stiffeners 50 at their insides, towards the rest of the fabric. In this case the closed loop strands 30 would tend to move inwardly towards the rest of the fabric and the generally U-shaped deviations 12 would tend to close or compress. In this situation, it might be best to use the generally S-shaped deviations 11 as disclosed in FIG. 2 since they are more readily compressible than the generally U-shaped deviations 12.

The fabric 5 of FIG. 5 employs a pair of corrugated circumferential defining strands 40 at the bell-forming end thereof. These corrugated strands 40 are expandable longitudinally so that an enlarged bell can be formed on a generally cylindrical cage made of the fabric 5. The longitudinal defining strands and the stiff eners 50 are welded to the corrugated circumferentials 40 at the null points 42 thereof. The points 42 are referred to as null points since they lie approximately half-way between the nodes 43 of the corrugated strands 40. As forces of elongation are placed on corrugated strands 40, the outer nodes 43 tend to move inwardly towards the rest of the fabric while the inner nodes 43 tend to move outwardly away from the rest of the fabric.

Fabric 5 includes a plurality of tie rods 60 joined to corrugated strands 40 at the corresponding nodes thereof. The tie rods 60 are not joined to any of the non-expandable circumferential defining strands 20. In this way, the tie rods 60 are free to move inwardly and outwardly as the corrugated strands 40 are expanded. The tie rods 60 act as anchors after the fabric is embedded in concrete to prevent further elongation or expansion of corrugated strands 40. The construction and operation of such tie rods is more fully set forth and is claimed in my copending patent application Ser. No. 330,609, entitled FABRIC AND METHOD FOR FORMING PIPE REINFORCEMENT.

The fabric 6 shown in FIG. 6 is comparable to the fabric 1 of FIG. I except that only a single closed loop circumferential strand 30 is employed, and its loops 31 are approximately half the size of the loops 31 of the fabric in FIG. 1. Further, the longitudinals 10 are provided with generally U-shaped deviations 12 which serve to ease formation of the bell endof the fabric in the manner set forth in my copending patent application Ser. No. 330,605, entitled METHOD AND FAB- RIC FOR PIPE REINFORCEMENT.

The fabric 7 set forth in FIG. 7 is comparable to that disclosed in FIG. 1 except thata longitudinally expandable circumferential strand 45 is employed immediately adjacent the bell-forming end of the fabric, the bell-forming end of the fabric being defined by the closed loop circumferentials 30. Circumferential strand 45 includes a plurality of generally U-shaped deviations 46 therein, one between each pair of adjacent longitudinals I0 and stiffeners 50. Because the stiffeners 50 are somewhat stiffer than longitudinals l0, and because they must be bent outwardly during the formation of the bell on the fabric cage, the stiffeners 50 tend to resist expansion of the bell. The provision in the first circumferential strand adjacent the bell of a deviation between each stiffener 50 and its adjacent longitudinal 10 provides for just enough expansion of that first circumferential to ease the resistance of the stiffeners 50 to bending and thereby'render the task of forming the bell somewhat easier. Yet, the use of a sparing number of such deviations in the first circumferential strand adjacent the bell prevents its wholesale elongation. If the elongation were too excessive, the cage would not fit properly within a pipe form.

The alternative embodiment fabric 8 shown in FIG. 8 is comparable to the fabric 5 of FIG. 5 in that'a pair of corrugated circumferential defining strands 40 are employed at the bell-formingend of the fabric. However, no ,tie rods 60 are employed and the stiffeners 50 are welded to the-corrugatedstrands 40 at their nodes 43. In order to compensate for the fact that the nodes 43 must move as the corrugated circumferentials 40 are expanded, the stiffeners 50 are provided with generally S-shaped deviations 51 which are capable of cifabric is then formed into a generally cylindrical cage,

either circular or elliptical, and the free ends of the fabric are welded together. The longitudinally expandable strands at the bell-forming end of the cage, either closed loop circumferentials 30 or corrugated circumferentials 40, are expanded radially outwardly to define an enlarged hell on the end of the cage. The specific manner in which the various strands of wire interact have been fully set forth above. With the bell end formed, the entire cage is placed in a form or packer head apparatus and concrete is cast in around the cage.

The stiffeners 50 provide substantial stiffening for the pipe at the bell end thereof. They aid in preventing the longitudinally expandable circumferentials from expanding further after the pipe has been completed and placed in the ground. They resist the tendency which the bell end of the pipe has to collapse when dirt is piled in on top of it. Thus, the pipe made from a fabric made in accordance with this invention is considerably stronger than prior art pipes made from fabric capable of being expanded radially outwardly to form the bell of the fabric.

Of course, it is understood that the above is merely a preferred embodiment of the invention and that various changes and alterations can be made without departing from the spirit and broader aspects of the invention. 1

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows.

1. In a fabric for reinforcing concrete pipe or the like, said fabric including a plurality of rigidly connected longitudinal and circumferential defining strands, at least one of said circumferential defining strands at the bell-forming end of the fabric being expandable longitudinally of itself, the improvement in said fabric comprising: a plurality of stiffener members interposed between various ones of said longitudinal defining strands and extending generally parallel to said longitudinal defining strands, said stiffener members being generally shorter than said longitudinal defining strands; said stiffener members being rigidly joined to at least one non-longitudinally expandable circumferential defining strand and being rigidly joined to all said longitudinally expandable circumferential strands whereby when said fabric is formed into a cage with an expanded bell, said stiffener members aid in minimizing collapsing of said bell end when weight is placed on a pipe containing such a cage.

2. The fabric of claim I in which said stiffener members are connected to the first two non-longitudinally expandable circumferential strands. V

3. The fabric of claim 2 in which there are at least two said longitudinally expandable circumferential strands at the bell-forming end of the fabric.

4. The fabric of claim 3 in which said stiffeners are made of a material which is stiffer than that of which said longitudinal defining strands are made.

5. The fabric of claim 1 in which said stiffeners are made of a material which is stiffer than that of which said longitudinal defining strands are made.

6. The fabric of claim 1 in which said longitudinally expandable circumferential strands each comprise a plurality of interconnected expandable closed loops; said stiffener members being joined to said closed loop circumferentials intermediate said loops whereby said stiffeners do not interfere with the expansion of said closed loops.

7. The fabric of claim 6 in which said longitudinal defining strands are also joined to said closed loop circumferentials intermediate said loops thereof whereby said longitudinal defining strands do not interfere with expansion of said closed loops.

8. The fabric of claim 6 in which said longitudinal defining strands are joined to said closed loop circumferential strands at both apexes of a given closed loop, said longitudinal defining strands including a collapsible deviation therein located between the opposite sides of said given loop whereby when said loop is expanded longitudinally, said collapsible deviation collapses and said sides of said given loop collapse towards one another.

9. The fabric of claim 6 in which said stiffener members are operably joined to the first two nonlongitudinally expandable circumferential defining strands of said fabric; said fabric including at least two expandable circumferential strands at said bell end thereof.

10. The fabric of claim 9 in which said longitudinal defining strands are also joined to said closed loop circumferentials intermediate said loops thereof whereby said longitudinal defining strands do not interfere with expansion of said closed loops.

11. The fabric of claim 9 in which said longitudinal defining strands are joined to said closed loop circumferential strands at both apexes of a given closed loop, said longitudinal defining strands including a collapsible deviation therein located between the opposite sides of said given loop whereby when said loop is expanded longitudinally, said collapsible deviation collapses and said sides of said given loop collapse towards one another.

12. The fabric of claim 1 in which said longitudinally expandable circumferential strands each comprise a plurality of interconnected expandable closed loops; each said stiffener being joined to each said expandable circumferential at a closed loop thereof, said stiffener being joined to both of the opposing sides of said loop; said stiffener including a collapsible deviation therein positioned within said closed loop, between said opposing sides, whereby when said closed loop is expanded, said deviation collapses and said sides are free to collapse towards one another.

13. The fabric of claim 12 in which said stiffener members are operably joined to the first two nonlongitudinally expandable circumferential defining strands of said fabric; said fabric including at least two expandable circumferential strands at said bell end thereof.

14. The fabric of claim 1 in which said expandable circumferential defining strands each comprise a plurality of interconnected expandable closed loops; each of said stiffeners being joined to said expandable circumferentials on a closed loop thereof, said stiffener being joined to only one of the two opposing sides of said closed loop whereby the other of said sides is free to collapse towards the said one joined side when said circumferential defining strand is expanded.

15. The fabric of claim 14 in which said longitudinal defining strands are joined to said expandable circumferentials intermediate said closed loop thereof; said longitudinals including deviations therein generally at the bell-forming end of the fabric whereby movement of the free sides of said loops towards the sides joined to said stiffeners is facilitated by the collapsing or elongation of said deviation.

16. The fabric of claim 15 in which said stiffeners are joined to that side of a given closed loop which is spaced away from the non-longitudinally expandable cicumferentials of the fabric.

17. The fabric of claim 15 in which said stiffener members are operably joined to the first two nonlongitudinally expandable circumferential defining strands of said fabric; said fabric including at least two expandable circumferential strands at said bell end thereof.

18. The fabric of claim 14 in which said stiffener members are operably joined to the first two nonlongitudinally expandable circumferential defining strands of said fabric; said fabric including at least two expandable circumferential strands at said bell end thereof.

19. The fabric of claim 1 in which said expandable circumferential defining strands are corrugated, said stiffeners being joined to said corrugated circumferential defining strands on the null points thereof.

20. The fabric of claim 19 which includes a plurality of tie members joined only to said corrugated circumferential defining strands, each tie member joining a corresponding set of nodes of said corrugated circumferential defining strands, there being at least two said corrugated circumferential defining strands.

21. The fabric of claim 20 in which said longitudinal defining strands are joined to said corrugated circumferential defining strands on null points thereof.

22. The fabric of claim 21 in which said stiffener members are operably joined to the first two nonlongitudinally expandable circumferential defining strands of said fabric; said fabric including at least two expandable circumferential strands at said bell end thereof.

23. The fabric of claim 19 in which said stiffener members are operably joined to the first two nonlongitudinallyexpandable circumferential defining strands of said fabric; said fabric including at least two expandable circumferential strands at said bell end thereof.

24. The fabric of claim 1 in which said expandable circumferential defining strands are corrugated, said stiffeners being joined to said corrugated circumferentials at nodes thereof; said stiffeners including nonrectilinear deviations therein generally at the bellforming end of the fabric whereby said stiffeners can contract or elongate as the nodes to which they are joined move towards or away from the non-expandable circumferential defining strands.

25. The fabric of claim 24 in which said longitudinal 4 defining strands are joined to said corrugated circumferentials at the null points thereof.

26. The fabric of claim in which said stiffener members are operably joined to the first two nonlongitudinally expandable circumferential defining strands of said fabric; said fabric including at least two expandable circumferential strands at said bell end thereof.

27. The fabric of claim 24 in which said stiffener members are operably joined to the first two nonlongitudinally expandable circumferential defining strands of said fabric; said fabric including at least two expandable circumferential strands at said bell end thereof.

28. In a fabric for reinforcing concrete pipe or the like, said fabric including a plurality of longitudinal and circumferential defining strands, at least one circumferential defining strand at the bell-forming end of the fabric comprising a plurality of interconnected closed loops expandable longitudinally of said one strand, the improvement comprising: each said longitudinal defining strand being joined to said closed loop circumferential strand at a closed loop thereof, said longitudinal defining strand extending across said loop and being joined to each side thereof; said longitudinal defining strand including a collapsible deviation therein located between said opposite sides within said loop whereby when said closed loop circumferential strand is expanded, said collapsible deviation collapses allowing said opposite sides of said closed loop to collapse towards one another.

29. The fabric of claim 28 in which there are at least two said longitudinally expandable circumferential strands at the bell-forming end of the fabric.

30. In a fabric for reinforcing concrete pipe or the like, said fabric including a network of interconnected, laterally disposed strands of wire or the like, the improvement in said fabric comprising: at least one circumferential defining strand formed of a plurality of interconnected closed loops expandable longitudinally thereof; a plurality of strands joined to said closed loop circumferential defining strands and extending generally laterally thereto; at least some of said plurality of strands being joined to said closed loop circumferential strands at said closed loops thereof, extending generally across said loop; each said strand being joined at a closed loop and extending across said closed loop being joined to both sides of said closed loop and including-a compressible deviation located within saidloop between said sides thereof whereby when said closed loop' circumferential strand is longitudinally expanded, thereby allowing said opposite sides of said closed loop to collapse towards one another.

said compressible deviation compresses 31. The fabric of claim 30 in which said compressible deviation is generally S-shaped.

32. The fabric of claim 30 in which there are at least two said longitudinally expandable circumferential strands at the bell-forming end of the fabric.

33. In a fabric for reinforcing concrete pipe or the like, said fabric including a network of interconnected, laterally disposed strands of wire or the like, the improvement in said fabric comprising: at least one circumferential defining strand formed of a plurality of interconnected closed loops expandable longitudinally thereof; a plurality of strands joined to said closed loop circumferential defining strand and extending generally laterally thereof; some of said lateral strands extending. across a closed loop, others being joined to said cir-.

cumferential defining strand intermediate said closed loops; those extending across said closed loop being joined to only one side thereof whereby the other of said sides is free to collapse towards said one joined side when said circumferential defining strand is expandable and those joined intermediate said loops including a deviation therein which can be either compressed or expanded whereby movement of the free sides of said loops towards the sides joined to said stiffeners is facilitated by the collapsing or elongation of said deviation.

34. The fabric of claim 33 in which there are at least two said longitudinally expandable circumferential strands at the bell-forming end of the fabric.

35. In a fabric for reinforcing concrete pipe or the like, said fabric including a network of interconnected,

laterally disposed strands of wire or the like, the improvement in said fabric comprising: at least one circumferential defining strand at the bell-forming end of said fabric being generally corrugated; a plurality of strands joined to said corrugated strand and extending generally laterally thereof; some of said laterally extending strands being joined to said corrugated strand at the null points thereof and others being joined to said corrugated strands generally at the nodes thereof; those strands joined to the nodes of said corrugated strands including generally S-shaped deviations thereincapable of expansion or compression whereby as said corrugated strand is expanded during formation of .a bell on a cylindrical cage formed of said fabric, said nodes are free to move either inwardly or outwardly with respect to the rest of said fabric through the compression or expansion of said generally S-shaped deviations.

36. The fabric of claim 35 in which there are at least two said longitudinally expandable circumferential 

1. In a fabric for reinforcing concrete pipe or the like, said fabric including a plurality of rigidly connected longitudinal and circumferential defining strands, at least one of said circumferential defining strands at the bell-forming end of the fabric being expandable longitudinally of itself, the improvement in said fabric comprising: a plurality of stiffener members interposed between various ones of said longitudinal defining strands and extending generally parallel to said longitudinal defining strands, said stiffener members being generally shorter than said longitudinal defining strands; said stiffener members being rigidly joined to at least one non-longitudinally expandable circumferential defining strand and being rigidly joined to all said longitudinally expandable circumferential strands whereby when said fabric is formed into a cage with an expanded bell, said stiffener members aid in minimizing collapsing of said bell end when weight is placed on a pipe containing such a cage.
 2. The fabric of claim 1 in which said stiffener members are connected to the first two non-longitudinally expandable circumferential strands.
 3. The fabric of claim 2 in which there are at least two said longitudinally expandable circumferential strands at the bell-forming end of the fabric.
 4. The fabric of claim 3 in which said stiffeners are made of a material which is stiffer than that of which said longitudinal defining strands are made.
 5. The fabric of claim 1 in which said stiffeners are made of a material which is stiffer than that of which said longitudinal defining strands are made.
 6. The fabric of claim 1 in which said longitudinally expandable circumferential strands each comprise a plurality of interconnected expandable closed loops; said stiffener members being joined to said closed loop circumferentials intermediate said loops whereby said stiffeners do not interfere with the expansion of said closed loops.
 7. The fabric of claim 6 in which said longitudinal defining strands are also joined to said closed loop circumferentials intermediate said loops thereof whereby said longitudinal defining strands do not interfere with expansion of said closed loops.
 8. The fabric of claim 6 in which said longitudinal defining strands are joined to said closed loop circumferential strands at both apexes of a given closed loop, said longitudinal defining strands including a collapsible deviation therein located between the opposite sides of said given loop whereby when said loop is expanded longitudinally, said collapsible deviation collapses and said sides of said given loop collapse towards one another.
 9. The fabric of claim 6 in which said stiffener members are operably joined to the first two non-longitudinally expandable circumferential defining strands of said fabric; said fabric including at least two expandable circumferential strands at said bell end thereof.
 10. The fabric of claim 9 in which said longitudinal defining strands are also joined to said closed loop circumferentials intermediate said loops thereof whereby said longitudinal defining strands do not interfere with expansion of said closed loops.
 11. The fabric of claim 9 in which said longitudinal defining strands are joined to said closed loop circumferential strands at both apexes of a given closed loop, said longitudinal defining strands including a collapsible deviation therein located between the opposite sides of said given loop whereby when said loop is expanded longitudinally, said collapsible deviation collapses and said sides of said given loop collapse towards one another.
 12. The fabric of claim 1 in which said longitudinally expandable circumferential strands each comprise a plurality of interconnected expandable closed loops; each said stiffener being joined to each said expandable circumferential at a closed loop thereof, said stiffener being joined to both of the opposing sides of said loop; said stiffener including a collapsible deviation therein positioned within said closed loop, between said opposing sides, whereby when said closed loop is expanded, said deviation collapses and said sides are free to collapse towards one another.
 13. The fabric of claim 12 in which said stiffener members are operably joined to the first two non-longitudinally expandable circumferential defining strands of said fabric; said fabric including at least two expandable circumferential strands at said bell end thereof.
 14. The fabric of claim 1 in which said expandable circumferential defining strands each comprise a plurality of interconnected expandable closed loops; each of said stiffeners being joined to said expandable circumferentials on a closed loop thereof, said stiffener being joined to only one of the two opposing sides of said closed loop whereby the other of said sides is free to collapse towards the said one joined side when said circumferential defining strand is expanded.
 15. The fabric of claim 14 in which said longitudinal defining strands are joined to said expandable circumferentials intermediate said closed loop thereof; said longitudinals including deviations therein generally at the bell-forming end of the fabric whereby movement of the free sides of said loops towards the sides joined to said stiffeners is facilitated by the collapsing or elongation of said deviation.
 16. The fabric of claim 15 in which said stiffeners are joined to that side of a given closed loop which is spaced away from the non-longitudinally expandable cicumferentials of the fabric.
 17. The fabric of claim 15 in which said stiffener members are operably joined to the first two non-longitudinally expandable circumferential defining strands of said fabric; said fabric including at least two expandable circumferential strands at said bell end thereof.
 18. The fabric of claim 14 in which said stiffener members are operably joined to the first two non-longitudinally expandable circumferential defining strands of said fabric; said fabric including at least two expandable circumferential strands at said bell end thereof.
 19. The fabric of claim 1 in which said expandable circumferential defining strands are corrugated, said stiffeners being joined to said corrugated circumferential defining strands on the null points thereof.
 20. The fabric of claim 19 which includes a plurality of tie members joined only to said corrugated circumferential defining strands, each tie member joining a corresponding set of nodes of said corrugated circumferential defining strands, there being at least two said corrugated circumferential defining strands.
 21. The fabric of claim 20 in which said longitudinal defining strands are joined to said corrugated circumferential defining strands on null points thereof.
 22. The fabric of claim 21 in which said stiffener members are operably joined to the first two non-Longitudinally expandable circumferential defining strands of said fabric; said fabric including at least two expandable circumferential strands at said bell end thereof.
 23. The fabric of claim 19 in which said stiffener members are operably joined to the first two non-longitudinally expandable circumferential defining strands of said fabric; said fabric including at least two expandable circumferential strands at said bell end thereof.
 24. The fabric of claim 1 in which said expandable circumferential defining strands are corrugated, said stiffeners being joined to said corrugated circumferentials at nodes thereof; said stiffeners including non-rectilinear deviations therein generally at the bell-forming end of the fabric whereby said stiffeners can contract or elongate as the nodes to which they are joined move towards or away from the non-expandable circumferential defining strands.
 25. The fabric of claim 24 in which said longitudinal defining strands are joined to said corrugated circumferentials at the null points thereof.
 26. The fabric of claim 25 in which said stiffener members are operably joined to the first two non-longitudinally expandable circumferential defining strands of said fabric; said fabric including at least two expandable circumferential strands at said bell end thereof.
 27. The fabric of claim 24 in which said stiffener members are operably joined to the first two non-longitudinally expandable circumferential defining strands of said fabric; said fabric including at least two expandable circumferential strands at said bell end thereof.
 28. In a fabric for reinforcing concrete pipe or the like, said fabric including a plurality of longitudinal and circumferential defining strands, at least one circumferential defining strand at the bell-forming end of the fabric comprising a plurality of interconnected closed loops expandable longitudinally of said one strand, the improvement comprising: each said longitudinal defining strand being joined to said closed loop circumferential strand at a closed loop thereof, said longitudinal defining strand extending across said loop and being joined to each side thereof; said longitudinal defining strand including a collapsible deviation therein located between said opposite sides within said loop whereby when said closed loop circumferential strand is expanded, said collapsible deviation collapses allowing said opposite sides of said closed loop to collapse towards one another.
 29. The fabric of claim 28 in which there are at least two said longitudinally expandable circumferential strands at the bell-forming end of the fabric.
 30. In a fabric for reinforcing concrete pipe or the like, said fabric including a network of interconnected, laterally disposed strands of wire or the like, the improvement in said fabric comprising: at least one circumferential defining strand formed of a plurality of interconnected closed loops expandable longitudinally thereof; a plurality of strands joined to said closed loop circumferential defining strands and extending generally laterally thereto; at least some of said plurality of strands being joined to said closed loop circumferential strands at said closed loops thereof, extending generally across said loop; each said strand being joined at a closed loop and extending across said closed loop being joined to both sides of said closed loop and including a compressible deviation located within said loop between said sides thereof whereby when said closed loop circumferential strand is longitudinally expanded, said compressible deviation compresses thereby allowing said opposite sides of said closed loop to collapse towards one another.
 31. The fabric of claim 30 in which said compressible deviation is generally S-shaped.
 32. The fabric of claim 30 in which there are at least two said longitudinally expandable circumferential strands at the bell-forming end of the fabric.
 33. In a fabric for reinforcing concrete pipe or the like, said fabric includinG a network of interconnected, laterally disposed strands of wire or the like, the improvement in said fabric comprising: at least one circumferential defining strand formed of a plurality of interconnected closed loops expandable longitudinally thereof; a plurality of strands joined to said closed loop circumferential defining strand and extending generally laterally thereof; some of said lateral strands extending across a closed loop, others being joined to said circumferential defining strand intermediate said closed loops; those extending across said closed loop being joined to only one side thereof whereby the other of said sides is free to collapse towards said one joined side when said circumferential defining strand is expandable and those joined intermediate said loops including a deviation therein which can be either compressed or expanded whereby movement of the free sides of said loops towards the sides joined to said stiffeners is facilitated by the collapsing or elongation of said deviation.
 34. The fabric of claim 33 in which there are at least two said longitudinally expandable circumferential strands at the bell-forming end of the fabric.
 35. In a fabric for reinforcing concrete pipe or the like, said fabric including a network of interconnected, laterally disposed strands of wire or the like, the improvement in said fabric comprising: at least one circumferential defining strand at the bell-forming end of said fabric being generally corrugated; a plurality of strands joined to said corrugated strand and extending generally laterally thereof; some of said laterally extending strands being joined to said corrugated strand at the null points thereof and others being joined to said corrugated strands generally at the nodes thereof; those strands joined to the nodes of said corrugated strands including generally S-shaped deviations therein capable of expansion or compression whereby as said corrugated strand is expanded during formation of a bell on a cylindrical cage formed of said fabric, said nodes are free to move either inwardly or outwardly with respect to the rest of said fabric through the compression or expansion of said generally S-shaped deviations.
 36. The fabric of claim 35 in which there are at least two said longitudinally expandable circumferential strands at the bell-forming end of the fabric. 